On September 29, 2017 9:58:41 PM GMT+02:00, Sebastian Pop <seb...@gmail.com>
wrote:
>On Fri, Sep 29, 2017 at 2:37 PM, Sven Verdoolaege
><sven.verdoola...@gmail.com> wrote:
>> [Sorry for the resend; I used the wrong email address to CC Alex]
>>
>> On Wed, Sep 27, 2017 at 02:18:51PM +0200, Richard Biener wrote:
>>> Ah, so I now see why we do not perform interchange on trivial cases
>like
>>>
>>> double A[1024][1024], B[1024][1024];
>>>
>>> void foo(void)
>>> {
>>> for (int i = 0; i < 1024; ++i)
>>> for (int j = 0; j < 1024; ++j)
>>> A[j][i] = B[j][i];
>>> }
>>
>> I didn't see you mentioning _why_ you expect an interchange here.
>> Are you prehaps interested in spatial locality?
>> If so, then there are several approaches for taking
>> that into account.
>> - pluto performs an intra-tile loop interchange to
>> improve temporal and/or spatial locality. It shouldn't
>> be too hard to do something similar on an isl generated
>> schedule
>> - Alex (Oleksandr) has been working on an extension of
>> the isl scheduler that takes into account spatial locality.
>> I'm not sure if it's publicly available.
>> - I've been working on a special case of spatial locality
>> (consecutivity). The current version is available in
>> the consecutivity branch. Note that it may get rebased and
>> it may not necessarily get merged into master.
>>
>> There are also other approaches, but they may not be that
>> easy to combine with the isl scheduler.
>
>Would the following work?
>Add to the proximity relation the array accesses from two
>successive iterations of the innermost loop:
>A[j][i] -> A[j][i+1] and B[j][i] -> B[j][i+1]
>With these two extra relations in the proximity map,
>isl should be able to interchange the above loop.
Can anyone give a hint on how to do that in ISL terms?
Richard.
>Sebastian
